Mechanical characteristics of tensile strength ratio method compared to other parameters used for moisture susceptibility evaluation of asphalt mixtures

In this study, mechanical characteristics of tensile strength ratio (TSR) were evaluated by comparing it to other methods in evaluating moisture sensitivity of asphalt mixtures. Twenty types of asphalt mixtures with and without anti-stripping additives were prepared and tested in the laboratory. Uniaxial compressive strength (UCS) and indirect tensile (IDT) testing were conducted to determine the mixture's tensile strength ratio and cohesion ratio (CR). Determining TSR alone was found to be insufficient when evaluating moisture resistance. There is a need to consider both TSR and wet IDT strength to properly evaluate moisture behavior of asphalt mixtures. Moreover, it was found that the cohesion and the IDT strength have a good relation in which the minimum condition of the slope, must be met. However, it was observed that β values change depending on material type and temperature. Hence, there is a need to evaluate these β values for varying material and testing temperature. In addition, it was found that the TSR and CR results are highly correlated with an average difference of 1.5%. Furthermore, other tests such as Marshall stability and dynamic immersion were also conducted. It was found that Marshall stability ratio (MSR) and Marshall stability to flow ratio (MSFR) values are less sensitive to moisture effect when measuring moisture resistance compared to TSR values. Finally, the 48 h testing result of the dynamic immersion test showed better correlation with TSR values.